This project is to increase the understanding of the acid proteases; their common structural features and catalytically reactive residues. The acid protease of Rhizopus chinensis will be separated into its two isoelectric forms, the amino acid sequence will be determined for the major form and a comparative structure for the minor form. The disulfide pairing will be identified. The diazo and epoxide reactive aspartyls will be identified along with the amino acid sequences of the surrounding peptide. We will examine these data in comparison with other acid protease structures and reach a conclusion on the extent of common structural features and the constancy of their catalytic aspartyls. The strategy for the sequence determination is conventional. Methionine cleavage fragments, tryptic peptides, chymotrypsin overlaps, Edman degradation, amino and carboxypeptidases will be utilized to obtain linear sequence.